AstraZeneca's Mystic trial hits another snag, delaying Imfinzi's lung cancer expansion

AstraZeneca hit a pothole last year when its immuno-oncology drug Imfinzi fell short in a closely watched lung cancer trial, Mystic. But company executives looked on the bright side: Just because the therapy didn’t hit its goal for staving off cancer growth didn’t mean it wouldn’t later prove it could help patients live longer.

And later just got even later. AstraZeneca said Monday that overall survival results from Mystic wouldn’t come through the first half of this year as planned. Instead, that all-important data will be ready to go in the second half.

That doesn’t seem like much of a delay. But competition in lung cancer is fierce these days, and Merck & Co.’s Keytruda has a big head start. It was the first PD-1/L1 checkpoint inhibitor to nab an FDA approval for previously untreated non-small cell lung cancer patients—without diagnostic testing up front—and has since scored a follow-up approval in combination with chemotherapy, another immunotherapy first.

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The Mystic delay could actually mean that Imfinzi—or Imfinzi plus AstraZeneca’s experimental med tremelimumab, a combo that makes up one arm of the three-arm study—is performing better than expected. It’s an event-driven trial, so it only wraps up after enough patients have died to make the data set big enough to analyze. It’s continuing, as the company points out, “as per protocol.

There’s no way to know for sure, however, until the trial analysis wraps up. Until then, Keytruda has a clear route to continued growth in the first-line treatment setting. Bristol-Myers Squibb’s Opdivo failed its own trial in previously untreated patients, and Roche’s first-line data on Tecentriq wasn’t a clear victory, analysts say—and besides, it made its debut in December, just three months ago.

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But that’s not to say AstraZeneca hasn’t had its own victories with Imfinzi lately. Last month, the drug snagged an FDA green light in previously treated, stage 3 lung cancer patients whose tumors can't be removed, a market without a single competitor in sight.

That's an entirely new experience for Imfinzi, the fifth-to-market PD-1/L1 immunotherapy, which faces four other contenders in its only other approved indication, bladder cancer.

With those rivals years away from gaining a similar nod in lung cancer, Imfinzi could hit $1 billion in worldwide sales from that indication alone, Leerink Partners analyst Seamus Fernandez has predicted. Bernstein’s Tim Anderson has estimated that the opportunity in the world's top seven markets tallies about 47,000 patients.